Japanese Patent Application Laid-Open Publication No. H6-140563 (Patent document 1) describes that a groove or a projecting part is formed in a side surface of a die pad on which a semiconductor chip is mounted.
Also, Japanese Patent Application Laid-Open Publication No. H10-4170 (Patent document 2) describes that a discontinuous groove is formed in a chip mounting part of a lead frame on which a semiconductor chip is mounted.
Further, Japanese Patent Application Laid-Open Publication No. H8-107172 (Patent document 3) describes that concave-convex parts are formed on the surface of leads arranged in the periphery of a semiconductor chip.